The invention relates to the field of electrical connectors. More specifically, the invention relates to an interposer for connecting a ball grid array to a substrate.
The recent drive for smaller, more functional electronic equipment has created an ongoing need for miniaturization of all components, especially electrical connectors. The drive for smaller electronic equipment has also been accompanied by a recent preference for surface mount techniques (SMT) for mounting components on circuit boards. To satisfy the need for increased terminal density in SMT, array connectors have been created. In particular, as described in U.S. Pat. No. 6,024,584, entitled xe2x80x9cHigh Density Connector,xe2x80x9d and incorporated herein by reference, ball grid array (BGA) connectors have become a reliable and efficient technique for mounting high-density electrical connectors on substrates using SMT.
BGA connectors have an insulative connector housing. One side of the connector housing are a matrix of spherical solder balls positioned to engage the conductive paths of a circuit substrate. The opposite side of the connector housing has a corresponding matrix of contact terminals, which extend through the connector housing and connect electrically to the solder balls. These contact terminals are designed to engage another BGA connector, similarly connected to another substrate, thus permitting board-to-board interconnection via the BGA connector device. The connection between the BGA and the circuit substrates is accomplished by a process called xe2x80x9creflow.xe2x80x9d In the reflow process, the solder balls are heated until they begin to melt and then cooled such a soldered connection is made between the BGA and the substrate. Because the circuit substrate typically is a flat surface with etched circuits, the solder balls substantially maintain their position during the reflow process.
Often, when using the BGA to interconnect circuit substrates, an interposer also is used. An interposer is an intermediate connection device that may be placed between the BGA connector and the circuit substrate. By using an interposer to connect and disconnect the BGA and the circuit substrate, wear on the BGA connector and substrate""s etched circuit interface is reduced. Also, the interposer may provide an alternative connection means with the substrate. Unlike the substrate interface, however, the interposer may not provide a flat mating surface for the BGA""s solder balls. For example, the interposer also may be an array of solder balls, similar to the BGA connector. As a result, during the reflow process the BGA-to-interposer connection may shift, causing improper connection. Interposers also allow for better heat absorption and heat transfer away from delicate electronic circuit elements by keeping the heat within the interposer.
Therefore, there is a need to provide an interposer, BGA connector, or other connection device that can more easily mate with the BGA connector or other similar connector.
The invention includes an interposer, BGA connector, or other connection device that provides electrical contact with a ball grid array connector. The inventive interposer includes a housing with contacts. The contacts have a first end and a second end. The interposer also includes a first body and a second body of reflowable, electrically conductive material disposed on the first end of at least one of the contacts. The first body and the second body provide an electrical contact between the interposer and a single body of reflowable, electrically conductive material of the ball grid array connector. The contacts may pass from a first face of the housing to a second face of the housing opposite the first face, such that the first end of the contacts are accessible on a first face of the housing and the second end of the contacts are accessible on an opposite face of the housing. The first body and the second body of the interposer form a soldered connection with the single body of reflowable, electrically conductive material of the ball grid array connector during a reflow process. The interposer also may include a third body of reflowable, electrically conductive material disposed on the first end of at least one of the contacts, where the third body provides electrical contact between the interposer and the single body of reflowable, electrically conductive material of the ball grid array connector, and provides a soldered connection with the ball grid array connector during a reflow process. One or more of the bodies may be substantially spherical and/or substantially conical, and may have substantially similar dimensions.